Identical Pumps

Identical Pumps

Operating two identical pumps in parallel the assumption is made that the flow will double. This however is not the case. In order to calculate the additional flow realized by running two identical pumps in parallel the following calculations must be made.

First let's look at the pump curve and system head curve with one pump running.

TDH	FLOW
130'	100 GPM
120'	190 GPM
110'	280 GPM
100	360 GPM
OPERATING POINT (A)
85'	470 GPM

Second let's look at the pump curve and system head curve with two pumps running.

TDH	FLOW
130'	200 GPM
120'	380 GPM
110'	560 GPM
100	720 GPM
OPERATING POINT (B)
105'	660 GPM

The addition of the second identical pump produces and extra 190 GPM and does not double the flow. Point C is the flow produced by each pump when both pumps are running.